Modulation is the alteration or modification of a carrier wave by another wave or signal. The amplitude and phase angle or frequency of the carrier wave may be modulated. Pulse-width modulation (PWM) is a type of pulse-time modulation (PTM) in which the time of occurrences of the leading edge or the trailing edge is varied from its unmodulated position. Wave samples are used to vary the time of occurrences of some parameters of the pulses. PWM uses a square wave whose duty cycle is modulated by changing the widths of pulses and information is encoded in the width of pulses.
PWM edges are typically created with a counter and comparator circuit that decodes counter values to set and reset a flip flop. The modulation of the PWM edges is limited by the clock rate at which the counter and comparator run at. A faster clock rate will provide more accurate modulation of PWM edges, which will in turn provide finer control of a device. The challenge in designing PWM circuits is then to minimize the time period that can be used for modulating the PWM edges as the tuning resolution is directly proportional to the clock rate of the circuit.
PWM may be used to control mechanical devices like electronic stepper motors where the motors are used in applications that require accurate positioning. These devices would generally benefit from finer controls. Therefore, it is highly desirable to have a PWM circuit with a faster clock rate in order to enhance the accuracy of any application or device that uses such modulation. It is in this context that embodiments of the present invention arise.